It is often desirable to apply roofing granules to roofing membranes by pressing the granules into a surface of the membranes. The granules are typically applied for various aesthetics and/or functional purposes, such as to provide ultraviolet (UV) protection and/or foot traffic protection for the asphalt and underlying membrane. Conventional granule application processes typical involve passing a roofing membrane and granules through a pair of press rollers to mechanically force the granules into the roofing membrane. The press rollers are typically small in diameter and apply a single point pressure to the roofing membrane and granules to force the granules into the roofing membrane.
This conventional process, however, is often less effective at pressing granules into roofing membranes that exhibit elastic behavior because the elastic behavior of such materials often causes the roofing membrane to deflect under the instant point load applied by the press rollers during the granule pressing process. This deflection may cause the roofing membrane to elastically rebound or return to an original position and force the granule out of a temporary pocket that is created by or during the granule pressing process. The result may be that a substantial portion of the granules do not properly adhere to the roofing membrane, which may instantly or quickly fall off as minor loads are applied to the roofing membranes and granules, such as by an object rubbing against the granules.